Notes on contributors

The gas-phase complex UO2(TMOGA)(2)(2+) (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700-1800 cm(-1) was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm(-1) (<1%) and a maximum deviation of 21 cm(-1) (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric v(3) mode, which appeared at 965 cm(-1) and was predicted by DFT as 953 cm(-1). This v(3) frequency is red-shifted relative to bare uranyl, UO22+, by ca. 150 cm(-1) due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO2(acetone)(4)(2+). The uranyl v(3) frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central O-ether, of TMOGA has been replaced by CH2. The computed v(3) for UO2(TMGA)(2)(2+), 950 cm(-1), is essentially the same as that for UO2(TMOGA)(2)(2+), suggesting that electron donation to uranyl from the ether of TMOGA is minor. The computed v(3) asymmetric stretching frequencies for the three actinyl complexes, UO2(TMOGA)(2)(2+), NpO2(TMOGA)(2)(2+) and PuO2(TMOGA)(2)(2+), are comparable. This similarity is discussed in the context of the relationship between v(3) and intrinsic actinide-oxygen bond energies in actinyl complexes

IRMPD spectroscopy reveals a novel rearrangement reaction for modified peptides that involves elimination of the N-terminal amino acid

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Variable Denticity in Carboxylate Binding to the Uranyl Coordination Complexes

Tris-carboxylate complexes of uranyl [UO2]2+ with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetato uranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric −CO2 stretches of the monodentate and bidentate acetate, CH3 bending and umbrella vibrations, and a uranyl O–U–O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the predominant conformer of the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate and two bidentate benzoate ligands

IRMPD spectroscopy b(2) ions from protonated tripeptides with 4-aminomethyl benzoic acid residues

Collision-induced dissociation (CID) of the peptide alanine-4-aminomethylbenzoic acid-glycine, A(AMBz)G generates a prominent b(2) ion despite a previous report [ER. Talaty, T.J. Cooper, S.M. Osburn, M.J. Van Stipdonk, Collision-induced dissociation of protonated tetrapeptides containing beta-alanine, gamma-aminobutyric acid, e-aminocaproic acid or 4-aminomethylbenzoic acid residues, Rapid Commun. Mass Spectrom. 20 (2006) 3443-3455] which showed that incorporation of the aromatic amino acid into a peptide sequence inhibits generation of b(n) ions formed by cleavage to the immediate C-terminal side of the residue. Infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations suggest that the b(2) ion generated from A(AMBz)G has an acylium structure. The b2 ion generated from (AMBz)AG, in which the aromatic residue is situated at the amino-terminus, is instead a conventional oxazolone. (c) 2012 Elsevier B.V. All rights reserved

Strategies to Improve Selection of Patients Without Typical Left Bundle Branch Block for Cardiac Resynchronization Therapy

Contains fulltext : 220974.pdf (Publisher’s version ) (Closed access)Cardiac resynchronization therapy (CRT) is becoming increasingly controversial in patients without typical left bundle branch block (LBBB). Yet, several recent studies displayed that a distinct subpopulation of patients with non-LBBB does benefit from CRT. Patients with non-LBBB should, therefore, not as a group be withheld from a potentially very beneficial therapy. Unfortunately, current clinical practice lacks validated selection criteria that may identify possible CRT responders in the non-LBBB subgroup. Consequently, clinical decision making in these patients is often challenging. A few studies, strongly differing in design, have proposed additive selection criteria for improved response prediction in patients with non-LBBB. There is accumulating evidence that more sophisticated echocardiographic dyssynchrony markers, taking into account the underlying electrical substrate responsive to CRT, can aid in the selection of patients with a non-LBBB who may benefit more favorably from CRT. Furthermore, it is important that cardiologists are aware of the shortcomings of current electrocardiographic selection criteria for CRT. Whereas these criteria provide an evidence-based approach for selecting patients for CRT, they do not necessarily guarantee the most optimal strategy for patient selection. Parameters obtained with vectorcardiography, such as QRS area, show potential to overcome the shortcomings of conventional electrocardiographic selection criteria and may improve response prediction regardless of QRS morphology

The gas-phase bis-uranyl nitrate complex [(UO2)2(NO3)5]-: Infrared spectrum and structure

The infrared spectrum of the bis-uranyl nitrate complex [(UO2)2(NO3)5]− was measured in the gas phase using multiple photon dissociation (IRMPD). Intense absorptions corresponding to the nitrate symmetric and asymmetric vibrations, and the uranyl asymmetric vibration were observed. The nitrate ν3 vibrations indicate the presence of nitrate in a bridging configuration bound to both uranyl cations, and probably two distinct pendant nitrates in the complex. The coordination environment of the nitrate ligands and the uranyl cations were compared to those in the mono-uranyl complex. Overall, the uranyl cation is more loosely coordinated in the bis-uranyl complex [(UO2)2(NO3)5]− compared to the mono-complex [UO2(NO3)3]−, as indicated by a higher O-U-O asymmetric stretching (ν3) frequency. However, the pendant nitrate ligands are more strongly bound in the bis-complex than they are in the mono-uranyl complex, as indicated by the ν3 frequencies of the pendant nitrate, which are split into nitrosyl and O-N-O vibrations as a result of bidentate coordination. These phenomena are consistent with lower electron density donation per uranyl by the nitrate bridging two uranyl centers compared to that of a pendant nitrate in the mono-uranyl complex. The lowest energy structure predicted by density functional theory (B3LYP functional) calculations was one in which the two uranyl molecules bridged by a single nitrate coordinated in a bis-bidentate fashion. Each uranyl molecule was coordinated by two pendant nitrate ligands. The corresponding vibrational spectrum was in excellent agreement with the IRMPD measurement, confirming the structural assignment